Method of securing metal fins to tubes



May 1, ma. A J. BERG @,668534 METHOD 0F SECURING METAL FINS TO TUBES Filed Q32. 6. 1926 2 Sheets-Sheet 1 May 1, 192s. 1,668,534

A. J. BERG 'METHOD OF SECURING METAL FINS T TUBES v Filed Aug. e. 192e z sheets-snee: 2

' increased.

l sive patterns and molding ap `Patented May 1, 1928.

UNI-TED ASTATES PATENT OFFICE.

ALRED J. BERG, OF PORTSMOUTH, NEW HAMPSHIRE, ASSIGNOR OF ONE-THIRD TO PAUL F. FOSTER, 0F THE UNITED STATES NAVY, AND ONE-THIRD- TO JOHN 0. HUSE, 0F BALTIMORE, MARYLAND. v

METHOD 0F SECURING- METAL FINS T0 TUBES,

Application led lAugust 6, 1926. Serial No. 127,692.

-My invention relates to a method and apparatus for securing flanges on tubes or cylinders,

4metal heat radiating and is a continuation-in-part of my application Serial No. 12,656 ined March 2, 1925.

The object of my invention is to provide l an effective yet inexpensive tool or apparatus for securing a stri periphery of a cy indrical member, the degree of heat transfer of metal about and in the whereby therebetween is plicable to quantity production.

Ak further object of my invention is to pro vide a irm fin-joint Ithat requires no brazing or soldering material or other additional securing means.

Heretofore in cylinders of the finned type,

to either cast the iin integral with the cyllnder or in the case ofit has been customary heat radiating strip is mechanically fastened to the tube or cylinder, to weld or braze the abutting surfaces together. The

casting method involves the disadvantage of expenproduction of brittle materia aratus and the .The welding and brazing method is slow, tedious and expensive and often rigid and eiiicient joint to allow transference of heat.

however, insures a My invention,

main body and contact between the radiatingfin at such a pressure as a most e` fails to give a suiciently a ready physical the heat to provide cient heat conducting joint and at the same time a mechanically strong joint su erior to welding. l

eference is to be had to the accompanyingl drawings forming a part of this specification in which like Yreference characters lindicate corresponding parts throughout the several views, and 1n which:

Figu

res 1, 2 and 3 represent, respectively,

the plan elevational and end views of m combined groove forming,

v Figures 4 and 5 show in detail and end views of the crim wheel,v

strip inserting too the sie.;

Figures 6, 7 8, and 9 il ustrate, in crosssection, several methods of operation for sev ,curing the iin within the groove, and

Figures 10 andV 11 show the end and side steel member 7 cut at one strip free to movelin a direction parallel to the tool body. The strip is guided in a vertical plane by passing it between iiat metal plates 13 and 14 attached to the'tool body by screws 15, plate 13 having a flat countersunk portion to accommddate the thickness of strip.

Reference character 4 designates a lead wheel preferably consisting of two metallic disks, spaced apart approximately the thickness of the ribbon or strip. These disks are free to rotate upon a bearing assing transversely to the `tool tbody tow ich it is at# tached by means ofithrust member 11 and screw 16. As shown in Fig. 1, this bearing is not normal to the length of tool body 7 but is placed at an angle thereto for reasons,

to be stated.

The crimp wheel, 5, shown in detail in Figs. 4 and 5, is made up `of two rotating disks secured together by means of screws 17, one of said disks held within the tool bod by thrust screw 12. The axis of rotation of t e crimp wheel is inclined, when considered in the vertical plane, causing the wheel to tilt upwardly, as best seen in Figure 1. As shown in Figure 4, I prefer to chamfer the two contacting surfaces of the crim wheel disks to such an angle as will loosel);r accommodate a lin after being placed ipon a tube.

The tool bo y proper consists of wrought end to fit a standpost and tapered in thickness at the to an angle coinciding with that defined by the space between the lead wheel disks which in' turn is determined by the horizontal progression of the lin along the surface of the cylinder.

ard tool other en having a bearing member v Intermediate the ends of tool bod( 7, see i llti 10 alines the back rest member 6 in a vertical plane. rlhis member has an arcuate portion cut out at one end corresponding to the curvature of the tube or cylinder 21 and is square threaded as shown by dotted line 18 to clear any burr raised in forming the grooves, as will be ex lained later. In addition to supporting t e tube it provides an inclined bearing surface for cutter l as best shown in Figure 3. j

Rigid connection is made between the tool body and member 6 by means of clamp screw 8 passing1 through slot 9. The tool body has an arcuate portion cut transversely to correspond with that in the back rest member, the combined arcs completing a circle having a diameter slightly larger than that of tube 2l.

At 19, I have indicated oil holes for lubri-V cating the bearing surfaces of the lead and crimp wheels.

The manner of operation of my device is as follows:

The tool body is rigidly fastened in the tool post of a standard lathe equipped with thread cutting gear. The tube or cylinder to be finned is placed between lathe centers in the usual manner. Upon the machine starting, the triple groove cutter is moved to cut into the cylinder the required depth.

This tool is of the stepped type, each successive cutter penetrating to a greater depth so that one passage completely'nishes the helical groove. The cutter may be of a shape to form a groove having parallel side walls as shown in Figure 8, or a groove having slightly divergent side walls as shown in Figure 6. The groove shown in Figure 8 is of greater width than the groove shown in Figure 6. width of the parent.

groove will later become a Also as will become apparent, t e

groove shown in Figure 6 may be formed with parallel side walls if desired.

As illustrated to advantage in Figure 2 the metal ribbon 3 may be led from a suitable carrier such as a spool or the like (not shown) and assed between the guide lates 13 and-14. he strip may be extende into the peripheral groove of lea-'d wheel 4, and with the tube 21 rotating in the proper direc tion, the operation of the apparatus may proceed. With the cutters or groove formers 1v arranged to provide a groove such as shown in Flgure 6, and the wheel 4 arranged so that its fin or strip receiving groove is in alignment with the spiral groove formed by the members 1, ,the wheel 4 operates to serve two purposes, first, that of bending the strip 3 to the contour of the tube 21, and secondly, that of forcing the inner edge of the strip 3 into the prepared groove. actions of the wheel 4 are carried out simultaneously as .clearly illustrated in Figure 2. In fact, it may be said, that the bending The purpose of increasing the d These Th operation of the strip occurs simultaneously With its insertion into the groove prepared in t-he tube. The bending of the strip into spiral form causes the inner edge thereof to thicken appreciably, which thickening takes place during the time the edge is being forced into 'the groove of the tube. rThis operation is best illustrated in Figures 6 and 7. As shown in these figures the strip 3 is inserted into the groove in tube 21 and as it is bent and as its inner edge is forced against the bottom ot the groove, the edge is upset and thickened, orcin the strip into intimate contact with the side walls of the groove. When certain materials of strip and tubes are used, the sides of the groove may be actually forced outward, as

shown particularly in Figure 7. The upset-` ting of the inneredge of the strip 3 forms an exceedingly tight joint between the tube and the fin. The union provided is in the form of a dove-tail joint. ates any possibility of the tube releasing the iin, and permits heat to pass from the tube to the fin with substantially the same rapidity or eliciency asin the case when the tin is made integral with the tube. The joint between the tube and iin or strip secured by the operation heretofore described is clearly illustrated in Figure 7.

By regulating the angular' relation of the wheel 4 to the groove in the tube 21. the manner in which the inner edge of the strip or fin engages the side walls of the groove may be controlled. If the wheel 4 is inclined as shownin Figure 2 the joint shown in Figure 8 may be obtained.

In this operation, the inner edge of the iin is turned upon itself as illustrated. This is ue to the reason that as the fin or strip 3 enters the roove, engages with a side wall of the groove and turns upon itself.

Itis also to be understood that the expansion 1n thickness of the metal about the inner edge of the strip is utilized in obtaining the joint shown in Figure 8. This expansion takes place while the fin is being pressed into the groove and during the period the inner edge of the fin is being turned uponl itself. The expansion of the metal about the inner edge of the fin or strip during the bending thereof added to the upsetting of the inner edge of the strip produces a joint between the tube and fin of great strength and durability.

The crimping wheel 5 follows the operation of the lead wheel 4. The wheel 5 straddles the iin and its eripheral edges exert a pressure against tlie metal of the tube lying adjacent to the sides of the fin. e pressure of the wheel 5 may be adjusted so that sufficient metal is depressed along the edges of the fin receiving groove of the tube to seal the outer side walls cf the The joint obvi-` the inner edge of the strip groove against the adjacent walls of. the fin as l shown to advantage'in Figure 7.

Suilicient pressure may be given wheel 5 to press the metal of the tube' adjacent to the side walls of the fin to the extent shown in Figure 9. In this latter case the portion of the n contiguous with the outer edges of the groove is depressed and the metal about the inner edge of the iin further expanded. This added expansion of the metal about the inner edge of the iin presses outwardly to a greater degree the bottom portion of the Walls Aof the fin receiving groove and produces a joint similiar to that y shown in Figure 9. In this last mentioned method the joint between the fin and the tube, is strengthened. Also the joint produced has a high heat conducting eiciency, the same as is the case with the joints shown in changing the above relations.

Fi ures 7 and 8. y

n Figures 10 and 11, I have shown a section of a finned tube complete. At 20, I have indicated a series of prick-punch indentions equally spaced around the tube to .constitute a securing means additional to that gained by -knurlin or plain rolling. The use of these in entions is purely optional. i

vWhile I have shown and described speeifie shapes of joints obtained by a definite relation between the diameter of the lead and crimp Wheels with res ect to that of the tube, in addition to the re ative positionsof the wheels and the pressure with which they operate either upon the strip or the metal adjacent the strip, Vthe type of joint may be modified to meet a given condition by It is also apparent that the cutting vof groove ma be done by a tool separate and distinct rom the strip laying device or the knurler.

I do not limit or confine myself to the recise details of construction and method of opera-tion herein described and deline.- ated, as modification and variation may be made within the s'co out departing from t e spirit of the invention.

e of the claims with-- The product herein and produced by this method forms the sub'ect matter of my co-` pending application, berial No.251,589 and the apparatus shown-.herein forms the sub ject matter of my copendin application, Serial No. 249,404, divisiona applications hereof.

Havin thus described my invention what I c aim is:

l. The method of forming a heat radiator tube` which comprises forming a groove about the tube, inserting an edge of a strip into the groove, and upsetting the edge of the strip against the sides of the groove.

2. The method of forming a heat radiator tube which comprises forming a groove about the tube, and inserting an edge of the strip into the groove and upsetting the edge of the strip within the groove.

3. The method of forming a heat radiator tube which comprises forming a groove about the tube, inserting an edge of a strip into the groove, upsetting the edge of the vstrip against the sides of the groove and crimping the edges of the groove- 4. The method of providing a tube with a heat radiating fin which comprises forming a continuous groove about the tube, inserting an and upseting the edge of the iin against the bottom and the sides of the groove.

5. The method of providing a tube with a heat radiating fin which comprises forming a, groove about the tube, inserting an edge of a fin into the groove at an angle to engave a side wall of the oove, and upsetting t ie edge of the fin within the roove.

6.- The method of forming a heat radiator .tubel which 'consists in forming a groove edge of the in into the groove, 

